I live in an area that had over about 6 weeks with us pm2.5 aqi above 300 almost every day and many days exceeding 400 and it shocks me how many people still don't have filters of any kind and see this kind of DIY fan as excessive and silly. Ok, more filters for me I suppose.

Not sure how this helps. As soon as your kid sneezes near you, you're gonna catch covid. Air quality seems like a solid usage but in your house vs covid/flu? Your fan is gonna lose. Covid from outside your home? It's a non-issue and doesn't happen.

> As soon as your kid sneezes near you, you're gonna catch covid

That isn't for sure. Last I checked (over a year ago, so different variants) 50% of spouses sleeping together didn't catch COVID.

We are reasonably sure that amount of virus particles you are exposed to is a factor on if you will get COVID. So the more you can eliminate the better your odds are.

Delta is at least twice as virulent as the old strains.

'Masks', as worn by most, are assuredly not.

Edit: I'm not anti-mask. I would love it if you explained how ill-fitting cloth in a single pass is better than multi-pass HEPA or equivalent filtration rather than (or even as well as) down-voting, though.

Sure, yeah.

A simple cloth mask doesn't really protect the wearer; it protects others from the wearer. It slows droplets down as you exhale them. So they travel X feet, instead of X+Y feet. Depending on air currents and other variables the level of protection this offers others will range from "nothing at all" to "some".

Obviously, a HEPA filter is orders of magnitude better. But, is there a HEPA filter directly between you and the person next to you in line at the supermarket?

> A simple cloth mask doesn't really protect the wearer; it protects others from the wearer.

Sure. I'd call that 'different' rather than 'better', but I suppose it's subjective.

> Obviously, a HEPA filter is orders of magnitude better.

You would think, and yet my comment saying so, objecting to 'masks are better than an air filter' (when qualified to ill-fitting cloth as worn by most) is apparently highly objectionable.

> But, is there a HEPA filter directly between you and the person next to you in line at the supermarket?

Not a comparison I made, but yeah, if I went to a supermarket (I'm not, because I almost entirely had groceries delivered pre-pandemic, so now easily enough entirely) I would wear an FFP3 dust mask rather than ill-fitting cloth, which is two nines to HEPA's 3.5.

(More than that is probably not justified since fit won't be perfect, some leakage. Industrially etc. where there's a need for greater filtration I expect that's when you have to step up to fully enclosed hoods. I digress..)

   > Not a comparison I made

Sure, but it's the relevant one.

   > if I went to a supermarket [...] I would wear an FFP3 dust mask 
   rather than ill-fitting cloth, which is two nines to HEPA's 3.5.

Good. That would be very safe. Ideally everybody would do that. I'll let you think about how feasible that is.

I mean, your entire argument seems to be that cloth masks aren't perfect, I guess?

They sure aren't. But that's not the claim anybody is making. The evidence-backed claim is that they are better than nothing -- and "doing absolutely nothing" is apparently the hill that hundreds of millions of Americans have chosen to (literally) die upon We are trying to take a step forward from that, via a simple harm-reduction method that almost anybody can afford.

Let me ask you something. How effective would a public health measure need to be before you'd endorse it?

1%? 10%? 99%? 100%?

There have been 40 million confirmed cases in America, and likely several times that amount in reality. Over half a million deaths. Each single percentage point improvement in prevention represents > 400,000K cases and > 6,000 deaths.

Anything is better than nothing. Even if half the air isn't filtered because of bad fit, that is still half the air that is filtered.